Any recommendation on what SD card to install? I have birdseye satellite installed and would like to download several locations (6-8), with each location about 20 sq miles. Newbie.
You'll want to install a microSD datacard, not a "SD card". I used Kingston microSD HD class 10 cards and never had a problem with heavy use. Some of the folks I work with have used lower cost cards and seem to run into problems after about a year, so they end up paying more for the cheaper cards in both money & time waisted. As far as capacity, the eTrex will use up to a 32GB card, but in practice, 16 GB should be plenty as that GOS doesn't have a camera.
I did some "back of the envelope" quick calculations regarding Birdseye file sizes back in 2010 when they first rolled it out. Using the highest quality imagery, I came up with about 2.5MB per square mile. This could vary significantly based on the nature of the imagery due to the type of compression used. But 8 blocks of 20 square miles each would work out to about 400MB, so you won't need much of a memory card for that. You could even put it into internal memory.
I have a 16Gb class 10 card that I've filled completely with Birdseye and used on both a Montana and Oregon. When that card is inserted, the device seems to take FOREVER to start up. Maybe a minute or so. Personally, I found that unacceptable - especially if your GPS crashes for some reason while you are navigating. It will then take a long time to get back up and navigating.
So I only load small areas of Birdseye on the GPS when needed and keep all the big files archived on my computer.